Locking couplings are well known. Such couplings comprise a male endpiece, a female endpiece, an outer collar or groove of the male endpiece, and an abutment that is movable transversely in the wall of the female endpiece to be received in the groove or behind the collar of the male endpiece when it is in place in the female endpiece.
Some such devices include an indicator for showing whether or not the connection has been made correctly, so as to reduce the risks associated with poor coupling.
Because couplings are made of plastics material, the safety of such connections is limited to applications in hydraulic or pneumatic circuits at medium pressure. Unfortunately, in particular in the automobile industry, there exist fluid circuits in which operating pressures are becoming higher and higher.